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                                                                     EXHIBIT 4.3

                                                                  EXECUTION COPY


                    COLLATERAL PLEDGE AND SECURITY AGREEMENT

                             Dated February 1, 2002

                                      From

                            OSI PHARMACEUTICALS, INC.

                                   AS PLEDGOR

                                       to

                              THE BANK OF NEW YORK

                                   AS TRUSTEE

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                                TABLE OF CONTENTS

<Table>
<S>           <C>                                                                                     <C>
Section 1.    Grant Of Security........................................................................2

Section 2.    Security For Obligations.................................................................3

Section 3.    Maintaining The Pledged Account..........................................................3

Section 4.    Delivery And Control Of Collateral.......................................................3

Section 5.    Release Of Amounts.......................................................................5

Section 6.    Representations And Warranties...........................................................5

Section 7.    Further Assurances.......................................................................6

Section 8.    Covenants................................................................................8

Section 9.    Post-Closing Changes.....................................................................8

Section 10.   Transfers And Other Liens................................................................8

Section 11.   Trustee Appointed Attorney-In-Fact.......................................................8

Section 12.   No Assumption Of Duties; Reasonable Care.................................................9

Section 13.   Remedies................................................................................10

Section 14.   Indemnity And Expenses..................................................................11

Section 15.   Security Interest Absolute..............................................................11

Section 16.   Amendments; Waivers.....................................................................12

Section 17.   Notices; Etc............................................................................12

Section 18.   Continuing Security Interest; Assignments Under The Indenture...........................13

Section 19.   Termination.............................................................................13

Section 20.   Execution In Counterparts...............................................................13

Section 21.   Governing Law; Submission To Jurisdiction; Waiver Of Jury Trial.........................13

Schedule I    Pledged Security Entitlements
Schedule II   Osi Pharmaceuticals

EXHIBIT A     FORM OF CONTROL AGREEMENT
</Table>

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                    COLLATERAL PLEDGE AND SECURITY AGREEMENT

          COLLATERAL PLEDGE AND SECURITY AGREEMENT dated February 1, 2002 made
by OSI Pharmaceuticals, Inc., a Delaware corporation (the "PLEDGOR"), to The
Bank of New York, a New York Banking Corporation, in its capacity as Trustee
(the "TRUSTEE") for the holders (the "HOLDERS") of the Notes (as defined
herein), issued by the Pledgor under the Indenture referred to below.
Capitalized terms used and not defined herein have the meanings set forth or
referred to in the Indenture.

                             PRELIMINARY STATEMENTS

          (1)  The Pledgor and the Trustee have entered into that certain
Indenture dated as of February 1, 2002 (said Indenture, as it may hereafter be
amended, amended and restated, supplemented or otherwise modified from time to
time, being the "INDENTURE") pursuant to which the Pledgor is issuing on the
date hereof $200,000,000 aggregate principal amount of 4% Convertible Senior
Subordinated Notes due 2009.

          (2)  The Pledgor has security entitlements (the "PLEDGED SECURITY
ENTITLEMENTS") with respect to (i) the United States Treasury securities
identified on Schedule I hereto, and credited to the Pledgor's account, Account
No. 341431 (the "PLEDGED ACCOUNT"), with the Trustee at its office at 101
Barclay Street, New York, NY 10286 and (ii) all other financial assets credited
from time to time to the Pledged Account (such other financial assets, together
with the Pledged Security Entitlements, the "PLEDGED FINANCIAL ASSETS").

          (3)  To secure the obligations of the Pledgor under the Indenture and
the Notes to pay in full each of the first six scheduled interest payments on
the Notes and to secure repayment of the principal and interest on the Notes in
the event that the Notes become due and payable prior to such time as the first
six scheduled interest payments thereon shall have been paid in full
(collectively, the "OBLIGATIONS"), the Pledgor has agreed (i) to pledge to the
Trustee for its benefit and the ratable benefit of the Holders of the Notes, a
security interest in the Collateral (as defined herein) and (ii) to execute and
deliver this Pledge Agreement in order to secure the payment and performance by
the Pledgor of all of the Obligations.

          (4)  It is a condition precedent to the initial purchase of the Notes
by the initial Holders thereof that the Pledgor shall have granted the security
interest and made the pledge contemplated by this Agreement.

          (5)  Unless otherwise defined in this Agreement or in the Indenture,
terms defined in Article 8 or 9 of the UCC (as defined below) and/or in the
Federal Book Entry Regulations (as defined below) are used in this Agreement as
such terms are defined in such Article 8 or 9 and/or the Federal Book Entry
Regulations. "UCC" means the Uniform Commercial Code as in effect, from time to
time, in the State of New York; PROVIDED that, if perfection or the effect of
perfection or non-perfection or the priority of any security interest in any
Collateral is governed by the Uniform Commercial Code as in effect in a
jurisdiction other

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than the State of New York, "UCC" means the Uniform Commercial Code as in effect
from time to time in such other jurisdiction for purposes of the provisions
hereof relating to such perfection, effect of perfection or non-perfection or
priority. The term "FEDERAL BOOK ENTRY REGULATIONS" means (a) the federal
regulations contained in Subpart B ("TREASURY/RESERVE AUTOMATED DEBT ENTRY
SYSTEM (TRADES)") governing book-entry securities consisting of U.S. Treasury
bonds, notes and bills and Subpart D ("ADDITIONAL PROVISIONS") of 31 C.F.R. Part
357, 31 C.F.R. Section. 357.2, Section. 357.10 through Section. 357.14 and
Section. 357.41 through Section. 357.44 and (b) to the extent substantially
identical to the federal regulations referred to in clause (a) above (as in
effect from time to time), the federal regulations governing other book-entry
securities.

          NOW, THEREFORE, in consideration of the premises and in order to
induce the initial Holders of the Notes to purchase the Notes, the Pledgor
hereby agrees with the Trustee for the ratable benefit of the Holders of the
Notes as follows:

          Section 1.  GRANT OF SECURITY

          The Pledgor hereby pledges to the Trustee, for the ratable benefit of
the Holders of the Notes, and hereby grants to the Trustee, for the ratable
benefit of the Holders of the Notes, a security interest in, such Pledgor's
right, title and interest in and to the following, in each case, as to each type
of property described below, whether now owned or hereafter acquired by such
Pledgor, wherever located, and whether now or hereafter existing or arising
(collectively, the "COLLATERAL"):

               (a)    the Pledged Account, all Pledged Security Entitlements
     with respect to all Pledged Financial Assets from time to time credited to
     the Pledged Account, and all Pledged Financial Assets, and all dividends,
     distributions, return of capital, interest, cash, instruments and other
     property from time to time received, receivable or otherwise distributed in
     respect of or in exchange for any or all of such Pledged Security
     Entitlements or such Pledged Financial Assets and all subscription
     warrants, rights or options issued thereon or with respect thereto, any
     such property not constituting "securities" as defined in the UCC to be
     treated as a financial asset pursuant to Article 8 of the UCC;

               (b)    all other securities, security entitlements and other
     financial assets from time to time acquired by the Pledgor pursuant to
     Article 12 of the Indenture;

               (c)    all proceeds of any and all of the Collateral (including,
     without limitation, proceeds, collateral and supporting obligations that
     constitute property of the types described in clauses (a) and (b) of this
     Section 1 and this clause (c) and, to the extent not otherwise included,
     all cash).

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          Section 2.  SECURITY FOR OBLIGATIONS

          The security interest granted by this Agreement secures the payment of
all the Obligations, whether for principal or interest, now or hereafter
existing under the Notes (all such Obligations being the "Secured Obligations").
Without limiting the generality of the foregoing, this Agreement secures the
payment of all amounts that constitute part of the Secured Obligations and would
be owed by the Pledgor to the Trustee or any Holder of the Notes but for the
fact that they are unenforceable or not allowable due to the existence of a
bankruptcy, reorganization or similar proceeding involving the Pledgor.

          Section 3.  MAINTAINING THE PLEDGED ACCOUNT

          So long as any Secured Obligation shall remain outstanding:

               (a)    The Pledgor will maintain separately the Pledged Account
     with the Trustee.

               (b)    The Trustee shall have sole right to direct the
     disposition of funds with respect to the Pledged Account; and it shall be a
     term and condition of the Pledged Account, notwithstanding any term or
     condition to the contrary in any other agreement relating to the Pledged
     Account, that, except as otherwise provided by the provisions of Section 5
     and Section 19, no amount (including, without limitation, interest on the
     Pledged Securities Entitlements or Pledged Financial Assets credited
     thereto) will be paid or released to or for the account of, or withdrawn by
     or for the account of, the Pledgor or any other Person from the Pledged
     Account.

               (c)    The Trustee may, at any time and without notice to, or
     consent from, the Pledgor, transfer, or direct the transfer of, funds from
     the Pledged Account to satisfy the Pledgor's obligations under the
     Indenture if an Event of Default (as hereinafter defined) shall have
     occurred and be continuing.

          The Pledged Account shall be subject to such applicable laws, and such
applicable regulations of the Board of Governors of the Federal Reserve System
and of any other appropriate banking or governmental authority, as may now or
hereafter be in effect.

          Section 4.  DELIVERY AND CONTROL OF COLLATERAL

               (a)    All cash, certificates or instruments representing or
     evidencing the Collateral shall be delivered to and held by or on behalf of
     the Trustee pursuant hereto and shall be in suitable form for transfer by
     delivery, or shall be accompanied by duly executed instruments of transfer
     or assignment in blank, all in form and substance satisfactory to the
     Trustee. The Trustee shall have the right, at any time in its discretion
     and without notice to the Pledgor, to transfer to or to register in the
     name of the Trustee or any of its nominees any or all of the Collateral. In
     addition, the Trustee shall have the right at any time to exchange
     certificates or instruments representing or evidencing the Collateral for
     certificates or instruments of smaller or larger denominations. Also, the
     Trustee shall have the right at any time to convert Collateral consisting
     of financial assets

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     credited to the Pledged Account to Collateral consisting of financial
     assets held directly by the Trustee, and to convert Collateral consisting
     of financial assets held directly by the Trustee to Collateral consisting
     of financial assets credited to the Pledged Account.

               (b)    With respect to any Collateral in which the Pledgor has
     any right, title or interest and that constitutes an uncertificated
     security, the Pledgor shall cause the issuer thereof either (i) to register
     the Trustee as the registered owner of such security or (ii) to agree in
     writing with the Pledgor and the Trustee that such issuer will comply with
     instructions with respect to such security originated by the Trustee
     without further consent of the Pledgor, such agreement to be in form and
     substance satisfactory to the Trustee.

               (c)    With respect to any Collateral in which the Pledgor has
     any right, title or interest and that constitutes a security entitlement in
     which the Trustee is not the entitlement holder, such Pledgor will cause
     the securities intermediary with respect to such security entitlement
     either (i) to identify in its records the Trustee as the entitlement holder
     of such security entitlement against such securities intermediary or (ii)
     to agree in an authenticated record with such Pledgor and the Trustee that
     such securities intermediary will comply with entitlement orders (that is,
     notifications communicated to such securities intermediary directing
     transfer or redemption of the financial asset to which such Pledgor has a
     security entitlement) originated by the Trustee without further consent of
     such Pledgor, such authenticated record to be in substantially the form of
     Exhibit A hereto or otherwise in form and substance satisfactory to the
     Trustee.

               (d)    Prior to or concurrently with the execution and delivery
     hereof and prior to the transfer to the Trustee of the Pledged Financial
     Assets, the Trustee shall establish the Pledged Account on its books as a
     separate account segregated from all other custodial or collateral accounts
     at its office. Upon transfer of the Pledged Financial Assets to the
     Trustee, as confirmed to the Trustee by the securities intermediary, the
     Trustee shall make appropriate book entries indicating that the Pledged
     Financial Assets have been credited to and are held in the Pledged Account.
     Subject to the other terms and conditions of this Agreement, all funds or
     other property held by the Trustee pursuant to this Agreement shall be held
     in the Pledged Account subject to the exclusive dominion and control of the
     Trustee and exclusively for the ratable benefit of the Holders of the Notes
     and segregated from all other funds or other property otherwise held by the
     Trustee.

               (e)    All Collateral shall be retained in the Pledged Account
     pending disbursement pursuant to the terms hereof.

               (f)    Concurrently with the execution and delivery of this
     Agreement, the Trustee is delivering to the Pledgor a duly executed Control
     Agreement (the "Control Agreement") in the form of Exhibit A hereto, and a
     certificate of an officer of the Trustee, confirming the Trustee's
     establishment and separate maintenance of the Pledged Account, its receipt
     and holding of the Pledged Financial Assets and the crediting of the
     Pledged Financial Assets to the Pledged Account, all in accordance with
     this Agreement.

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               (g)    Concurrently with the execution and delivery of this
     Agreement, the Pledgor is delivering to the Trustee financing statements,
     in form acceptable to the Trustee, for filing under the UCC in all
     jurisdictions as necessary or desirable in order to perfect and protect the
     security interest created by this Agreement, covering the Collateral
     described in this Agreement.

          Section 5.  RELEASE OF AMOUNTS

               (a)    On the due date of any of the first six scheduled interest
     payments on the Notes, the Trustee will release from the Pledged Account
     funds sufficient to provide for the payment of the interest on the Notes in
     accordance with the payment provisions of the Indenture to the Holders of
     the Notes from (and to the extent of) proceeds of the Pledged Financial
     Assets. Nothing in this Section 5 shall affect the Trustee's rights to
     apply the Collateral to the payments of amounts due on the Notes upon
     acceleration thereof.

               (b)    The Trustee shall liquidate Collateral in the Pledged
     Account in order to make any scheduled payment of interest pursuant to the
     Notes, unless there are sufficient funds in the Pledged Account on such
     interest payment date. The Trustee shall be entitled to sell any Collateral
     as contemplated hereunder prior to the maturity of such Collateral and the
     Pledgor shall be responsible for the costs and expenses of such sale.

               (c)    If at any time before the first six scheduled interest
     payments on the Notes have been paid in full, repayment of the principal
     amount of the Notes shall be accelerated under the Indenture, the Trustee
     shall liquidate all Collateral in the Pledged Account for payment to the
     Holders, subject to the automatic stay provisions of bankruptcy law, if
     applicable. Distributions from the Pledged Account will be applied first to
     any accrued and unpaid interest on the Notes and second, to the extent
     available, to the repayment of the outstanding principal of the Notes.

          Section 6.  REPRESENTATIONS AND WARRANTIES

          The Pledgor represents and warrants that:

               (a)    The execution and delivery by the Pledgor of, and the
     performance by the Pledgor of its obligations under, this Agreement will
     not contravene any provision of applicable law or the certificate of
     incorporation of the Pledgor or any material agreement or other material
     instrument binding upon the Pledgor or any of its subsidiaries or any
     judgment, order or decree of any governmental body, agency or court having
     jurisdiction over the Pledgor or any of its subsidiaries, or result in the
     creation or imposition of any lien on any assets of the Pledgor, except for
     the security interests granted under this Agreement.

               (b)    No consent of any other person and no approval,
     authorization, order of, action by, notice to, filing or qualification
     with, any governmental authority, regulatory body, agency or other third
     party is required (i) for the execution, delivery or performance by the
     Pledgor of this Agreement, (ii) for the grant by the Pledgor of the

                                        5
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     assignment, pledge and security interest created hereby, (iii) for the
     perfection or maintenance of the assignment, pledge and security interest
     created hereunder (including the first priority nature of such assignment,
     pledge and security interest), except for (A) the execution of the Control
     Agreement by the parties thereto and (B) the filing of financing statements
     under the Uniform Commercial Code, which financing statements have been
     delivered to the Trustee for filing or (iv) for the exercise by the Trustee
     of its rights provided for in this Agreement or the remedies in respect of
     the Collateral pursuant to this Agreement, except as may be required in
     connection with the disposition of any portion of the Collateral by laws
     affecting the offering and sale of securities generally.

               (c)    The Pledgor is the legal and beneficial owner of the
     Collateral free and clear of any Lien, claim, option or right of others,
     except for the security interest created under this Agreement. No effective
     financing statement or other instrument similar in effect covering all or
     any part of the Collateral or listing the Pledgor or any trade name of the
     Pledgor as debtor is on file in any recording office, except such as may
     have been filed in favor of the Trustee relating to this Agreement. The
     Pledgor has only the trade names listed on Schedule II hereto.

               (d)    This Pledge Agreement has been duly authorized and validly
     executed and delivered by the Pledgor and constitutes a valid and binding
     agreement of the Pledgor, enforceable against the Pledgor in accordance
     with its terms.

               (e)    Upon the transfer to the Trustee of the Pledged Financial
     Assets, in accordance with Section 4 above, the pledge and grant of a
     security interest in the Collateral pursuant to this Agreement for the
     benefit of the Trustee and the Holders of the Notes will constitute a valid
     and perfected first-priority security interest in such Collateral, securing
     the payment of the Secured Obligations, enforceable as such against all
     creditors of the Pledgor (and any persons purporting to purchase any of the
     Collateral from the Pledgor).

               (f)    There are no legal or governmental proceedings pending or,
     to the best of the Pledgor's knowledge, threatened to which the Pledgor or
     any of its subsidiaries is a party or to which any of the properties of the
     Pledgor or any such subsidiary are subject that would materially adversely
     affect the power or ability of the Pledgor to perform its obligations under
     this Agreement or to consummate the transactions contemplated hereby.

               (g)    The pledge of the Collateral pursuant to this Agreement is
     not prohibited by law or governmental regulation (including, without
     limitation, Regulations G, T, U, and X of the Board of Governors of the
     Federal Reserve System) applicable to the Pledgor.

               (h)    No Event of Default (as defined below) exists.

               (i)    The jurisdiction (for purposes of Section 8-110(e) of the
     UCC) of the Trustee and the Pledged Account is New York.

          Section 7.  FURTHER ASSURANCES

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               (a)    The Pledgor agrees that from time to time, at the expense
     of the Pledgor, the Pledgor will promptly execute and deliver, or otherwise
     authenticate, all further instruments and documents, and take all further
     action that may be necessary or desirable, or that the Trustee may request,
     in order to perfect and protect any pledge or security interest granted or
     purported to be granted by the Pledgor hereunder or to enable the Trustee
     to exercise and enforce its rights and remedies hereunder with respect to
     any Collateral. Without limiting the generality of the foregoing, the
     Pledgor will promptly with respect to Collateral of such Pledgor: (i) if
     any such Collateral shall be evidenced by a promissory note or other
     instrument or chattel paper, deliver and pledge to the Trustee hereunder
     such note or instrument or chattel paper duly indorsed and accompanied by
     duly executed instruments of transfer or assignment, all in form and
     substance satisfactory to the Trustee; (ii) execute or authenticate and
     file such financing or continuation statements, or amendments thereto, and
     such other instruments or notices, as may be necessary or desirable, or as
     the Trustee may request, in order to perfect and preserve the security
     interest granted or purported to be granted by the Pledgor hereunder; (iii)
     deliver and pledge to the Trustee for benefit of the Trustee and the
     Holders of the Notes certificates representing Collateral that constitutes
     certificated securities, accompanied by undated stock or bond powers
     executed in blank; (iv) take all action necessary to ensure that the
     Trustee has control of the Pledged Account; and (v) deliver to the Trustee
     evidence that all other action that the Trustee may deem reasonably
     necessary or desirable in order to perfect and protect the security
     interest created by the Pledgor under this Agreement has been taken. From
     time to time upon request by the Trustee, the Pledgor will, at the
     Pledgor's expense, cause to be delivered to the Trustee, for the benefit of
     the Trustee and the Holders of the Notes, an opinion of counsel, from
     outside counsel reasonably satisfactory to the Trustee, as to such matters
     relating to the transactions contemplated hereby as the Trustee may
     reasonably request.

               (b)    The Pledgor hereby authorizes the Trustee to file one or
     more financing or continuation statements, and amendments thereto, relating
     to all or any part of the Collateral, in each case without the signature of
     the Pledgor, and regardless of whether any particular asset described in
     such financing statements falls within the scope of the UCC. A photocopy or
     other reproduction of this Agreement or any financing statement covering
     the Collateral or any part thereof shall be sufficient as a financing
     statement where permitted by law. The Pledgor ratifies its authorization
     for the Trustee to have filed such financing statements, continuation
     statements or amendments filed prior to the date hereof.

               (c)    The Pledgor will furnish to the Trustee from time to time
     statements and schedules further identifying and describing the Collateral
     and such other reports in connection with the Collateral as the Trustee may
     reasonably request, all in reasonable detail.

               (d)    The Pledgor will promptly pay all costs incurred in
     connection with any of the foregoing within 45 days of receipt of an
     invoice therefor. The Pledgor also agrees, whether or not requested by the
     Trustee, to take all actions that are necessary to perfect or continue the
     perfection of, or to protect the first priority nature of, the Trustee's
     security interest in and to the Collateral, including the filing of all
     necessary

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     financing and continuation statements, and to protect the Collateral
     against the rights, claims of interests of third persons (other than any
     such rights, claims or interests created by or arising through the
     Trustee).

          Section 8.  COVENANTS

          The Pledgor covenants and agrees with the Trustee and the Holders of
the Notes that from and after the date of this Agreement until the earlier of
payment in full in cash of (x) each of the first six scheduled interest payments
due on the Notes under the terms of the Indenture or (y) all obligations due and
owing under the Indenture and the Notes in the event such obligations become due
and payable prior to payment of the first six scheduled interest payments on the
Notes:

               (a)    that (i) it will not (and will not purport to) sell or
     otherwise dispose of, or grant any option or warrant with respect to, any
     of the Collateral or its beneficial interest therein and (ii) it will not
     create or permit to exist any Lien or other adverse interest in or with
     respect to its beneficial interest in any of the Collateral (except for the
     security interest granted under this Agreement); and

               (b)    that it will not (i) enter into any agreement or
     understanding that restricts or inhibits or purports to restrict or inhibit
     the Trustee's rights or remedies hereunder, including, without limitation,
     the Trustee's right to sell or otherwise dispose of the Collateral or (ii)
     fail to pay or discharge any tax, assessment or levy of any nature with
     respect to its beneficial interest in the Collateral not later than five
     days prior to the date of any proposed sale under any judgments, writ or
     warrant of attachment with respect to such beneficial interest.

          Section 9.  POST-CLOSING CHANGES

               (a)    The Pledgor will not change its name, type of
     organization, jurisdiction of organization, organizational identification
     number or location from those set forth in this Agreement without first
     giving at least 30 days' prior written notice to the Trustee and taking all
     action required by the Trustee for the purpose of perfecting or protecting
     the security interest granted by this Agreement. If the Pledgor does not
     have an organizational identification number and later obtains one, it will
     forthwith notify the Trustee of such organizational identification number.

          Section 10. TRANSFERS AND OTHER LIENS

          The Pledgor agrees that it will not (i) sell, assign or otherwise
dispose of, or grant any option with respect to, any of the Collateral, or (ii)
create or suffer to exist any lien upon or with respect to any of the Collateral
except for the pledge, assignment and security interest created under this
Agreement.

          Section 11. TRUSTEE APPOINTED ATTORNEY-IN-FACT

          The Pledgor hereby irrevocably appoints the Trustee the Pledgor's
attorney-in-fact, with full authority in the place and stead of the Pledgor and
in the name of the Pledgor or

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otherwise, from time to time in the Trustee's discretion, to take any action and
to execute any instrument that the Trustee may deem necessary or advisable to
accomplish the purposes of this Agreement, including, without limitation:

               (a)    to ask for, demand, collect, sue for, recover, compromise,
     receive and give acquittance and receipts for moneys due and to become due
     under or in respect of any of the Collateral,

               (b)    to receive, indorse and collect any drafts or other
     instruments, documents and chattel paper, in connection with clause (a)
     above, and

               (c)    to file any claims or take any action or institute any
     proceedings that the Trustee may deem necessary or desirable for the
     collection of any of the Collateral or otherwise to enforce the rights of
     the Trustee with respect to any of the Collateral, and

               (d)    to pay or discharge any taxes or Liens levied or placed
     upon the Collateral that the Pledgor has failed to pay or discharge in
     accordance herewith, the legality or validity thereof and the amounts
     necessary to discharge the same to be determined by the Trustee in its sole
     discretion, and such payments made by the Trustee to become part of the
     Obligations of the Pledgor to the Trustee, due and payable immediately upon
     demand;

PROVIDED, HOWEVER, that the Trustee shall have no obligation to perform any of
the foregoing. The Trustee's authority under this Section 11 shall include,
without limitation, the authority to endorse and negotiate any checks or
instruments representing proceeds of Collateral in the name of the Pledgor,
execute and give receipt for any certificate of ownership or any document
constituting Collateral, transfer title to any item of Collateral, sign the
other documents deemed necessary or appropriate by the Trustee to preserve,
protect or perfect the security interest in the Collateral and to file the same,
prepare, file and sign the Pledgor's name on any notice of Lien, and to take any
other actions arising from or incident to the powers granted to the Trustee in
this Agreement. This power of attorney is coupled with an interest and is
irrevocable by the Pledgor.

          Section 12. NO ASSUMPTION OF DUTIES; REASONABLE CARE

          The powers conferred on the Trustee hereunder are solely to protect
the interest of the Trustee and the Holders of the Notes in the Collateral and
shall not impose any duty upon it to exercise any such powers. Except for the
safe custody of any Collateral in its possession and the accounting for moneys
actually received by it hereunder, the Trustee shall have no duty as to any
Collateral, (a) as to ascertaining or taking action with respect to calls,
conversions, exchanges, maturities, tenders or other matters relative to any
Collateral, whether or not the Trustee or any Holder of the Notes has or is
deemed to have knowledge of such matters, (b) as to the taking of any necessary
steps to preserve rights against any parties or any other rights pertaining to
any Collateral or (c) as to investing or reinvesting any of the Collateral or
any loss on any investment. The Trustee shall be deemed to have exercised
reasonable care in the custody and preservation of any Collateral in its
possession if such Collateral is accorded treatment substantially equal to that
which it accords its own property.

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          Section 13. REMEDIES

          If any Event of Default under the Indenture or default hereunder (any
such Event of Default or default being referred to in this Agreement as an
"EVENT OF DEFAULT") shall have occurred and be continuing:

               (a)    The Trustee may exercise in respect of the Collateral, in
     addition to other rights and remedies provided for herein or otherwise
     available to it, all the rights and remedies of a secured party upon
     default under the UCC (whether or not the UCC applies to the affected
     Collateral) and also may: (i) require the Pledgor to, and the Pledgor
     hereby agrees that it will at its expense and upon request of the Trustee
     forthwith, assemble all or part of the Collateral as directed by the
     Trustee and make it available to the Trustee at a place and time to be
     designated by the Trustee that is reasonably convenient to both parties;
     (ii) without notice except as specified below, sell the Collateral or any
     part thereof in one or more parcels at public or private sale, at any of
     the Trustee's offices or elsewhere, for cash, on credit or for future
     delivery, and upon such other terms as the Trustee may deem commercially
     reasonable; and (iii) exercise any and all rights and remedies of the
     Pledgor under or in connection with the Collateral, or otherwise in respect
     of the Collateral, including, without limitation, (A) withdraw, or cause or
     direct the withdrawal, of all funds with respect to the Pledged Account and
     (B) exercise all other rights and remedies with respect to the Collateral,
     including, without limitation, those set forth in Section 9-607 of the UCC.
     The Pledgor agrees that, to the extent notice of sale shall be required by
     law, at least ten days' notice to the Pledgor of the time and place of any
     public sale or the time after which any private sale is to be made shall
     constitute reasonable notification. The Trustee shall not be obligated to
     make any sale of Collateral regardless of notice of sale having been given.
     The Trustee may adjourn any public or private sale from time to time by
     announcement at the time and place fixed therefor, and such sale may,
     without further notice, be made at the time and place to which it was so
     adjourned.

               (b)    Any cash held by or on behalf of the Trustee and all cash
     proceeds received by or on behalf of the Trustee in respect of any sale of,
     collection from, or other realization upon all or any part of the
     Collateral may, in the discretion of the Trustee, be held by the Trustee as
     collateral for, and/or then or at any time thereafter applied (after
     payment of any amounts payable to the Trustee pursuant to Section 14) in
     whole or in part by the Trustee for the ratable benefit of the Holders of
     the Notes against, all or any part of the Secured Obligations, in such
     order as the Trustee shall elect. Any surplus of such cash or cash proceeds
     held by the Trustee and remaining after payment in full of all the Secured
     Obligations shall be paid over to the Pledgor or to whomsoever may be
     lawfully entitled to receive such surplus.

               (c)    The Trustee may, without notice to the Pledgor except as
     required by law and at any time after the occurrence of an Event of
     Default, charge, set-off and otherwise apply all or any part of the Secured
     Obligations against any funds held with respect to the Pledged Account or
     any part thereof.

                                       10
<Page>

               (d)    The Pledgor further agrees to do or cause to be done all
     such other acts as may be necessary to make such sale or sales of all or
     any portion of the Collateral pursuant to this Section 13 valid and binding
     and in compliance with applicable law. The Pledgor further agrees that a
     breach of any of the covenants contained in this Section 13 will cause
     irreparable injury to the Trustee and the Holders of the Notes, that the
     Trustee and the Holders of the Notes have no adequate remedy at law in
     respect of such breach and, as a consequence, that each and every covenant
     contained in this Section 13 shall be specifically enforceable against the
     Pledgor, and the Pledgor hereby waives and agrees not to assert any
     defenses against an action for specific performance of such covenants
     except for a defense that no Event of Default has occurred and is
     continuing.

          Section 14. INDEMNITY AND EXPENSES

               (a)    The Pledgor agrees to indemnify, defend and save and hold
     harmless the Trustee and its Affiliates and their respective officers,
     directors, employees, agents and advisors (each, an "INDEMNIFIED PARTY")
     from and against, and shall pay on demand, any and all claims, damages,
     losses, liabilities and expenses (including, without limitation, reasonable
     fees and expenses of counsel) that may be incurred by or asserted or
     awarded against any Indemnified Party, in each case arising out of or in
     connection with or resulting from this Agreement (including, without
     limitation, enforcement of this Agreement), except to the extent such
     claim, damage, loss, liability or expense is found in a final,
     non-appealable judgment by a court of competent jurisdiction to have
     resulted from such Indemnified Party's gross negligence or willful
     misconduct.

               (b)    The Pledgor will upon demand pay to the Trustee the amount
     of any and all reasonable expenses, including, without limitation, the
     reasonable fees and expenses of its counsel and of any experts and agents,
     that the Trustee may incur in connection with (i) the administration of
     this Agreement, (ii) the custody, preservation, use or operation of, or the
     sale of, collection from or other realization upon, any of the Collateral,
     (iii) the exercise or enforcement of any of the rights of the Trustee or
     the Holders of the Notes hereunder or (iv) the failure by the Pledgor to
     perform or observe any of the provisions hereof.

               (c)    Additionally, in acting hereunder the Trustee is entitled
     to all rights, privileges, protections, benefits and immunities provided to
     it under Section 7.02 of the Indenture.

          Section 15. SECURITY INTEREST ABSOLUTE

          The obligations of the Pledgor under this Agreement are independent of
the Secured Obligations or any other Obligations of the Pledgor under or in
respect of the Indenture or the Notes, and a separate action or actions may be
brought and prosecuted against the Pledgor to enforce this Agreement. All rights
of the Trustee and the Holders of the Notes and the pledge, assignment and
security interest hereunder, and all obligations of the Pledgor hereunder, shall
be irrevocable, absolute and unconditional irrespective of, and the Pledgor
hereby irrevocably waives (to the maximum extent permitted by applicable law)
any defenses it may now have or may hereafter acquire in any way relating to,
any or all of the following:

                                       11
<Page>

               (a)    any lack of validity or enforceability of any of this
     Agreement, the Indenture or the Notes or any other agreement or instrument
     relating thereto;

               (b)    any change in the time, manner or place of payment of, or
     in any other term of, all or any of the Secured Obligations or any other
     amendment or waiver of or any consent to any departure from any the
     Indenture or Notes or any other agreement or instrument relating thereto;

               (c)    any taking, exchange, release or non-perfection of any
     Collateral or any other collateral, for all or any of the Secured
     Obligations;

               (d)    any manner of application of any Collateral or any other
     collateral, or proceeds thereof, to all or any of the Secured Obligations,
     or any manner of sale or other disposition of any Collateral or any other
     collateral for all or any of the Secured Obligations or any other assets of
     the Pledgor;

               (e)    any change, restructuring or termination of the corporate
     structure or existence of the Pledgor;

               (f)    any other circumstance (including, without limitation, any
     statute of limitations) or any existence of or reliance on any
     representation by the Trustee or any Holder of the Notes that might
     otherwise constitute a defense available to, or a discharge of, the
     Pledgor.

          This Agreement shall continue to be effective or be reinstated, as the
case may be, if at any time any payment of any of the Secured Obligations is
rescinded or must otherwise be returned by the Trustee or any Holder of the
Notes or by any other Person upon the insolvency, bankruptcy or reorganization
of the Pledgor or otherwise, all as though such payment had not been made.

          Section 16. AMENDMENTS; WAIVERS

               (a)    No amendment or waiver of any provision of this Agreement,
     and no consent to any departure by the Pledgor herefrom, shall in any event
     be effective unless the same shall be in writing and signed by the Trustee,
     and then such waiver or consent shall be effective only in the specific
     instance and for the specific purpose for which given. No failure on the
     part of the Trustee or any Holder of the Notes to exercise, and no delay in
     exercising any right hereunder, shall operate as a waiver thereof; nor
     shall any single or partial exercise of any such right preclude any other
     or further exercise thereof or the exercise of any other right.

          Section 17. NOTICES; ETC.

          All notices and other communications provided for hereunder shall be
either (i) in writing (including telegraphic, telecopier or telex communication)
and mailed, telegraphed, telecopied, telexed or otherwise delivered or (ii) by
electronic mail (if electronic mail addresses are designated as provided below)
confirmed immediately in writing, in the case of the Pledgor

                                       12
<Page>

or the Trustee, addressed to it at its address specified in the Indenture or, as
to any party, at such other address as shall be designated by such party in a
written notice to the other parties. All such notices and other communications
shall, when mailed, telegraphed, telecopied, telexed, sent by electronic mail or
otherwise, be effective when deposited in the mails, delivered to the telegraph
company, telecopied, confirmed by telex answerback, sent by electronic mail and
confirmed in writing, or otherwise delivered (or confirmed by a signed receipt),
respectively, addressed as aforesaid; except that notices and other
communications to the Trustee shall not be effective until received by the
Trustee. Delivery by telecopier of an executed counterpart of any amendment or
waiver of any provision of this Agreement shall be effective as delivery of an
original executed counterpart thereof.

          Section 18. CONTINUING SECURITY INTEREST; ASSIGNMENTS UNDER THE
                      INDENTURE

          This Agreement shall create a continuing security interest in the
Collateral and shall (a) remain in full force and effect until the earlier of
the payment in full in cash of (i) each of the first six scheduled interest
payments due on the Notes under the terms of the Indenture and (ii) all
obligations due and owing under the Indenture and the Notes in the event such
obligations become due and payable prior to payment of the first six scheduled
interest payment on the Notes; (b) be binding upon the Pledgor, its successors
and assigns and (c) inure, together with the rights and remedies of the Trustee
hereunder, to the benefit of the Trustee and the Holders of the Notes and their
respective successors, transferees and assigns. Without limiting the generality
of the foregoing clause (c), any Holder may assign or otherwise transfer all or
any portion of its rights under the Indenture and the Notes to any other Person,
and such other Person shall thereupon become vested with all the benefits in
respect thereof granted to such Holder herein or otherwise, in each case as
provided in the Indenture.

          Section 19. TERMINATION

               (a)    Upon the earlier of the payment in full in cash of each of
     the first six scheduled interest payments due on the Notes under the terms
     of the Indenture and all Secured Obligations, the pledge and security
     interest granted hereby shall terminate and all rights to the Collateral
     shall revert to the Pledgor. Upon any such termination, the Trustee will,
     at the Pledgor's expense, execute and deliver to the Pledgor such documents
     as the Pledgor shall reasonably request to evidence such termination.

          Section 20. EXECUTION IN COUNTERPARTS

          This Agreement may be executed in any number of counterparts, each of
which when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement. Delivery of an executed
counterpart of a signature page to this Agreement by telecopier shall be
effective as delivery of an original executed counterpart of this Agreement.

          Section 21. GOVERNING LAW; SUBMISSION TO JURISDICTION; WAIVER OF JURY
                      TRIAL

          This Agreement shall be governed by, and construed in accordance with,
the laws of the State of New York. The Pledgor irrevocably waives all right to
trial by jury in any action,

                                       13
<Page>

proceeding or counterclaim (whether based on contract, tort or otherwise)
arising out of or relating to this Agreement or the actions of the Trustee in
the negotiation, administration, performance or enforcement hereof.

                                       14
<Page>

          IN WITNESS WHEREOF, the Pledgor has caused this Agreement to be duly
executed and delivered by its officer thereunto duly authorized as of the date
first above written.

                                              OSI PHARMACEUTICALS, INC.


                                              By /s/ ROBERT L. VAN NOSTRAND
                                                 --------------------------
                                                 Title: Vice President and
                                                        Chief Financial Officer


                                              THE BANK OF NEW YORK, as Trustee


                                              By /s/ JULIE SALOVITCH-MILLER
                                                 --------------------------
                                                 Title: Vice President

                                       15
<Page>

                                                               SCHEDULE I TO THE
                                        COLLATERAL PLEDGE AND SECURITY AGREEMENT

                          PLEDGED SECURITY ENTITLEMENTS

<Table>
<Caption>
          DESCRIPTION OF ASSET                       CUSIP NUMBER           FACE AMOUNT OF ASSET
          --------------------                       ------------           --------------------
<S>                                                   <C>                      <C>
US TREASURY BILLS                                     912795KU4                USD 4,000,000
US TREAS NTS SEC STRIPPED                             912833FR6                USD 4,000,000
US TREAS NTS SEC STRIPPED                             912833FS4                USD 4,000,000
UNITED STATES TREAS NT STRIPPED PRIN PMT              912820DJ3                USD 4,000,000
UNITED STATES TREAS NT STRP PRIN PMT                  912820BJ5                USD 4,000,000
US TREASURY BD STRIPPED                               912803AB9                USD 4,000,000
</Table>

                                       16
<Page>

                                                              SCHEDULE II TO THE
                                        COLLATERAL PLEDGE AND SECURITY AGREEMENT

                               OSI PHARMACEUTICALS